Electrical heating element



March 10,*1931. E 1 l W|EGAND 1,795,628

ELECTRCAL- HEATLNC- ELEMENT Original Fid l- 3l, 1923 mi @2mm www Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE EDWIN L. WIEGAND, F DOBMONT, PENNSYLVANIA ELECTRICAL HEATING ELEMENT Original application led Arugust teniber 24, 1925.

conducting material enveloping a resistor that is thoroughly diffused throughout the space between the walls. Preferably, end walls close the space between the tubular walls, and the end walls are desirably held in place by peening or flangin the ends of the tubular walls over the edge portions of the end walls.

Heating elements of the foregoing type are especially useful for application to pipes, cylinders, cores and the like .that are to be "heated, an example of its use being found in electric soldering irons, as `will hereinafter be more specifically pointed out.

The present case is a division of my former application Serial No. 660,294, iiledAu st 31, 1923, and whereon Letters Patent. glll'lo. 1,614,330 were issued January 11, 1927; and with respect to the generic invention disclosed in this and my former case, the general objects are to provide a durable, practically indestructible, simple and comparatively inexpensive yet highly efficient electrical heating element affording maximum heat emissivity.

The special purpose of the invention which constitutes the subject matter of this case is to provide an electrical heating element that is characterized by a hollow center and that is relatively long in an axial direction and is 40 peculiarly suited for application to pipes, cylinders, cores and the like, and wherein are attained the objects above enumerated.

Other objects and purposes will appear as I proceed vto describe the invention by refe'rence to the accompanying drawing wherein Fig. l is a perspective view of my` improved electrical heating element with its side broken away to reveal the resistor, and Fig. 2 shows the element in'central section and as incorporated in a soldering iron.

31, 1923, serial No. 660,294. Divided and .this application led Sep- Serial No. 58,241.

The element, which is shown as cylindrical in form, is comprised of an outer tubular wall 1 and an inner tubular wall 2 between which is highly compacted or compressed a bodyv or mass 3 of suitable granular refractory material having very eiiicient electrical insulating and heat conducting qualities. Embedded within this body or massof granvular refractory material is an electrical resistor 4, and its ends are shown as connected to terminals 5 whichhave their inner ends or bases supported by and within the mass or body 3.

End walls 6 and 7 close the space between the tubular walls 1 and 2 and are shown as secured in place by the peened over or flanged ends of the tubular walls. The end wall 6 coA has openings 8 for the accommodation of the terminals 5, andwashers 9 of mica or other suitable material surround the terminals and space them from the surrounding metal parts, the washers serving to close the openings 8.

yFrom the description thus far it will be seen that my present invention provides a sheathed element of the embedded resistor type that is simple of construction, is very strong land durable, andishighly eiiicient. The sheath or casing comprised of the walls 1, 2, 6 and 7 is of suitable comparatively thin, sheet metal; and while I do not limit myself to any particular ldnd of'refractory insulating material, one kind found especially suitable for the purpose is composed of magnesium or zirconium silicate, or aluminum oxide, either individually or possibly a -compound of them, together, when desirable, with a binding vmaterial such as clay to give the necessary plastlcity during fabrication and to effect homogeneity in the final product.

In Fig. 2,. where I have shown av practical application of the invention, 10 denotes the hollow head of a soldering iron or similar device that is closed at its rear endby a cap 11,

held in place by screws 12. A tubular handle" 13 joins the cap and providesl a conduit through which wires 14 are led into the head. A'n axial, cylindrical core 15 merges into the forwardly converging wall of the head 10 atl the point of the iron, and is of a size to lit within-the inner tubular lwall-1 of the-heating element. The element is clamped to the core, with its forward end engaging a shoulder 16 thereon, by a plate 17 that is drawn to'- ward theend of the core by a screw 18, threaded into and located centrally of the core. The wires 14 are suitably connected to the terminals 5. t

When electric current is directed through the resistor, heat generated within the element is transmitted by conduction` to the core 15 and by convection and radiation to the wall of the head, andthe heat ofthese parts, augmented by that radiated from the forward end wall 7 of the element, is concentrated in the point of the iron'where, obviously, the highest temperature is desired.

AIl" or some classes of work, one terminal may come out of each endof the'element; for others, as in the present illustration, both terminals may project from the same end; and, again, for other classes of work, one or both terminals may extend from the cylindrical surface of the element in any desired location. 1

Having thus described' Illy-invention, what I claim is 1. As a new article of manufacture, an elec trical heating element consisting of a rela-- tively thin sheet metal sheath comprising comparatively deep inner and outer tubular walls, said walls being spaced apart, a resistor diffused throughout the cavity enclosed by said walls and spaced from the walls, and a mass of-g'ranular refractory electrical insulating material of high heat conducting quality permanently filling the space between the re-v sistor and the sheath, the mass of insulating material with the resistor therein being highly compressed within the aforesaid cavity.

2. As a new article of manufacture, an elec-V trical heating element consisting of a relasaid tubular'walls,a resistor diffused throughtively thin sheet metal sheath comprising comparatively deep inner and outer tubular walls and end walls closing the space between said tubular walls,.a resistor diffused throughout the cavity enclosed by said. walls and spaced from the walls, and a mass of granular refractory `electrical insulating material of high heat conductingA quality permanently filling the space between the resistor and the sheath, the resistor being provided with terminals each accessible through an opening in the sheath, the mass of insulating material with the resistor therein being highly compressed within the aforesaid cavity.

3. As a new article of manufacture, an electrical heating. element consisting of a rela.-

tively` thin sheet metall sheath comprising comparatively deep inner and outer tubular walls and end walls closing the space between out the cavity enclosed by said walls and spaced from the walls, and a mass of granular 'refractory electrical insulating material per- `signature.

manently filling the space between the resistor Y and the sheath, the entire assembly being in a highly compacted state, the resistor being providedv with terminalsv each accessible through an opening in the sheath.

4. As a new article of manufacture, an electrical heating element consisting' of'a rela.-

. tively thin sheet metal sheath. comprising electrical insulating material of high heat conducting quality permanently filling the space between the resistor and the sheath, the

lresistor being provided with terminals eaich accessible through an opening in the sheath, the mass of insulating material with the resistor therein being highly compressed within the aforesaid cavi y 5. As a new article of manufapture, an electrical heatingelement consisting of a rela.-

tively thin sheet metal .sheath comprising'- comparatively deep inner and outer ,tubular walls and end walls-closing the space between said tubular walls, a resistor diffused throughout the cavityv enclosed by said' walls and spaced from thevwalls, amass of granular refractory electrical insulating material of high heat conducting quality permanently filling the space between the resistor and the sheath, and a terminal applied to each end of the resistor, the same being accessible through an opening in the sheath and having a part embedded in the refractory material.

In testimony whereof, I hereunto affix my EDWIN L. wIEeANn 

